“children do not own cars and do not drive cars and they do not contribute to the traffic, therefore they should be removed from the carpool scheme as their participation does not INCREASE the number of unused vehicles in the city.”

The argument is actually a special case of a more general argument:

“any person who does not own a car does not contribute to the traffic, therefore they can be removed from the carpool scheme as their participation in no way INCREASES the number of unused cars in the city.”

I think this argument is irrational and will actually lead to more people owning more cars. Let me explain why.

Let us imagine that there are two students’ flats on the outskirts of the city. In the flat A there are 4 girls, each of which is a driver and owns her own car. In the flat B, there are also four girls, but only one owns a car and she has a driving license. The other three do not own cars and may not have driving licenses. As before, we have a single parking spot left and all 8 girls decided to come to town. We have the following situations:

All girls from flat A came in their own cars. Cars on the road and trying to park: 4. Number of people trying to park: 4. Happiness if 1 car can park: 1 person. Unhappiness if the car cannot park: 4 people (3 are always unhappy: only 1 car can park – limited resource). Number of cars left unused: 0.

All girls from flat A came in a single car, leaving 3 cars by their flat. Cars trying to park: 1. Number of people trying to park: 4. Happiness if they can park: 4 people. Unhappiness if they cannot park: 4 people. Number of cars left unused: 3.

The driver from flat B came in her car, and all the 3 flatmates took a bus. Cars trying to park: 1. Number of people trying to park: 1. Happiness if the car can park: 1 person. Unhappiness if the car cannot park: 4 people (3 are always unhappy, taking the bus regardless). Number of cars left unused: 0.

All girls from flat B came in a single car. Cars trying to park: 1. Number of people trying to park: 4. Happiness if they can park: 4 people. Unhappiness if they cannot park: 4 people. Number of cars left unused: 0.

Remember, there is only 1 empty space left, so we have to decide who gets the preferential treatment. Who is entitled to use it, so that we maximise the happiness and the use of the limited resource (our one single parking space). Let us put any moral considerations aside and look exclusively into practicality of the scheme (in other words let us be free to discriminate).

In cases 1 and 3, if the driver is entitled to park, the overall happiness value would be 1, which is pretty poor. If we compare it to cases 2 and 4, where the happiness value is 4, we have a clear winner. Ride share works. Clearly, we should give preference to 2 and/or 4 by implementing carpool scheme and discourage single-occupant vehicle usage. A simple ride share scheme would eliminated any incentive for cases 1 and 3 to occur. Done. Easy.

Benefits of maximising unused cars

Now let us take a closer look into cases 2 and 4. These cases are almost exactly the same, but, in the case 2 we have 3 unused cars parked by the flat. So we could be tempted to claim that we could achieved MORE by giving preference to girls from flat A, because we have INCREASED the total number of unused vehicles in the city in this case. This claim is correct: in the case of flat A we have an increased number of unused cars in the city.

We have 2 possible ride share options to decide:

[A] We DO NOT give preference to Flat A. There is NO preference of WHO constitutes a Passenger.

[B] We DO give preference to Flat A. The preference is for DRIVERS who OWN their cars. Rationale: increased number of unused cars in the city.

The example above shows the paradox. Let us see what will happen, if we were not to give preference to flat A (option A above)? The following assertions would be true:

Girls from flat A have a strong incentive to sell their unused vehicles and share a single car for their commuting. If they cannot park or travel in special lanes why bother owning so many cars? Better to sell some of them and share a smaller number of cars for commuting and travel.

Girls from flat B would have strong incentive NOT TO PURCHASE vehicles for themselves. They would continue to share the single vehicle that they currently own in their flat.

Conversely, what will happen, if we were to give preference to flat A (option B above)? It would be correct to assume that:

Girls from flat A have now a strong incentive NOT to sell their cars. They need to OWN cars and NOT USE THEM to be able to participate in the scheme.

Girls from flat B have a strong incentive TO PURCHASE their own cars, and become drivers, so that they can start participating in the scheme.

The effect of option A and B above is quite the opposite to what it supposedly intend to do. It sends a message about benefits of car ownership and being a driver. Besides, the argument of maximising the number of unused vehicles is irrational and has nothing to do with a carpool scheme as such. Why should it matter how many cars are not being used? The goal is to have LESS cars on the roads, less cars parked by the properties, and less cars parked in the city. The goal is to have LESS cars. Period. Not to have MORE unused cars. Option B does not work. It provides incentive to increase the total number of cars.

Children revisited

So where does it leave the children? Flat B example is equivalent to the household with a single mother and 3 children. Same as flat B a “mom with kids” do not “leave” any unused car behind. So even if the argument was correct and there was a benefit of maximising the number of unused cars and restricting the scheme to drivers and car owners only, a flat with single mom and 3 kids would be indistinguishable to a flat with 4 adults out of which only 1 owns a car. Therefore, the Rule [1](a) restricting the age of the scheme participants is NOT justified by the argument itself, and it is illogical to claim that “children do not contribute to the traffic….”. Most passengers in the ride share scheme do not contribute to the traffic – this is what the scheme is.

Summary

Option A, even though does not directly reduces the number of unused vehicles, overall reduces the incentive for car ownership. And this is what I think what carpooling is all about. The only long term and rational choice is to chose option A, where car owners and drivers are not in any way treated preferentially. “Second passengers are considered any living person. Additional passengers may be adults, children or infants.”

If either of the parents can share their car with the children and take part in the scheme, the scheme would provide a strong incentive to encourage a single vehicle per household. If we take that out we encourage families to own multiple vehicles per household.

Everywhere else in the world the authorities made the rational choice of making “any living person” to constitute a passenger. Not only does it make perfect sense in the context of equality and human rights, but it makes sense in the context of what carpool scheme is all about too. Not in Dunedin.